Method of manufacturing a 2-layered flexible substrate

Abstract

A method of manufacturing a 2-layered flexible substrate includes forming an underlying metal layer on an insulation film with a deposition layer formed by a dry plating method using at least one of nickel, copper-nickel alloy, chromium and chromium oxide and a copper deposition layer formed by a dry plating method on the noted deposition layer, then forming a primary electric copper plated deposition layer on the underlying metal layer, then applying a treatment using at least one alkaline solution selected from inorganic alkaline solutions and organic alkaline solutions, then forming an electroless copper plated deposition layer as an intermediate metal layer on the primary electric copper plated deposition layer and, finally, forming a secondary electric copper plated deposition layer on the intermediate metal layer, thereby finally forming a copper conductor layer of 1 to 35 mu m thickness on the insulation film.

Description

1. Field of the InventionThe present invention concerns a method of manufacturing a 2-layered flexible substrate and, more specifically, it relates to a method of manufacturing a 2-layered flexible substrate capable of easily forming a copper conductor layer of more intact and adhesive property upon forming a copper conductor layer on an insulation film by adopting a dry plating method, an electroless plating method and an electric copper plating method.2. Statement of the Prior ArtSubstrates used for manufacturing flexible wiring boards are generally classified into a 3-layered flexible substrate in which a copper foil as a conductor layer is appended on an insulation film by using an adhesive and a 2-layered flexible substrate in which a copper conductor layer is formed directly on an insulation film without using an adhesive by a dry plating method or a wet plating method.In a case of using the 3-layered flexible substrate, a 3-layered flexible wiring board can be manufactured by...

AI Technical Summary

Benefits of technology

An object o f the present invention is to overcome the foregoing problems in the manufacture of a flexible wiring board by using a dry plating method, an electroless plating method and an electric plating method and provide a method of manufacturing a flexible wiring bo

Problems solved by technology

However, since the copper foil of such a reduced thickness has less rigidity and poor handlability, it has been adopted a method of once appending a reinforcing material such as an aluminum carrier to the copper foil to increase the rigidity, then appending the copper foil and the insulation film and then removing the aluminum carrier.

However, this method involves a problem of taking much labor and time and is poor in the operation efficiency.

Further, such a thin copper foil also involves a problem in view of manufacturing techniques that defects of film are increased due to scattering of the film thickness, pin holes or occurrence of crackings.

Further, as the thickness of the copper foil is decreased, manufacturing thereof becomes more difficult, which increases the manufacturing cost to lose the economical merit of the 3-layered flexible wiring boards because of increase in the manufacturing cost.

Particularly, since it has been an increasing demand recently for a wiring board having a wiring portions with such a narrow width and a narrow pitch that can not be manufactured unless a copper foil having a thickness of less than ten and several micrometers, for example, about of several micrometers, the wiring board using the 3-layered flexible substrate involves problems in view of the manufacturing cost as well as the technical problems described above.

However, although the exposed portion of the insulation film induced by the pinholes can be eliminated to some extent by this method, a plating solution used for the electroless copper plating or a pretreatment solution theref or penetrates through already formed pinholes of various sizes to a position between the insulation film and the underlying metal film, which brings about hindrance for the adhesion of the underlying metal layer and, thus, the adhesion of the conductor layer by electric plating to be formed subsequently, and this method cannot provide a satisfactory countermeasure.